Nintendo has opened the site for The Legend if Zelda: A Link Between Worlds. They have already released brand new gameplay footage and additional information on the dungeons and the items that we will be seeing in the game...
The Legend of Zelda: A Link Between Worlds will be taking up 5482 blocks on your SD card when downloading it from the Nintendo eshop. That's around to 685MB. If you really want to have the downloaded copy then you might want to consider purchasing a new SD card. At that point you may be better off with the physical copy of the game...